1. Field of the Invention
The present invention relates to a coin type cell with lead terminals.
2. Description of the Related Art
With the development of a coin type cell having good storage properties such as a coin lithium cell, this coin cell is used as a back-up electric source for an electrical device or appliance. To such a coin type cell, lead terminals are attached beforehand so as to make it easy to assemble the cell in a circuit base of the electrical device or appliance. In a conventional technique, as shown in FIG. 1, one end of a lead terminal 5 for a positive electrode is bonded to a positive electrode can 2, and one end of a lead terminal 6 for a negative electrode is spot welded to an upper surface of a central part of a negative electrode plate 3. The other end of each of the lead terminals 5 and 6 extends in a radial direction of a coin type cell 1 beyond an edge at which the negative electrode plate 3 and the positive electrode can 2 meet each other.
In an actual coin type cell, an opening edge 2a of the positive electrode can 2 reaches nearer to the upper surface of the negative electrode plate 3 than the distance seen in FIG. 1 which is an enlarged figure. Therefore, when a load is applied on an upper side of the lead terminal 6 for the negative electrode, the lead terminal 6 is bent and contacts the a periphery of the positive electrode can 2 to form a short circuit.
To prevent the formation of a short circuit through contact of the lead terminal 6 to the positive electrode can, 2 the periphery of the electrode can 2 is covered with an insulating tube 7, a front part of which is cut away (see, for example, Japanese Utility Model Kokai Publication No. 19145/1985).
However, the covering of the periphery of the positive electrode can 2 increases the production cost of the cell and decreases productivity.